Recording acoustic vibrations



Aug. 15, 1933. K/PULVERMACHER 1,922,821

RECORDING ACOUSTIC VIBRATIONS Filed Aug. 4, 1951 2 Sheets-Sheet 1 DH nnnnn n 2 1 I 2; Wm

idf] z ermac/zer 1933. K.' PULVERMACHER 1,922,821

RECORDING ACOUSTIC VIBRATIONS Filed Aug. 4, 1951 2 Sheets-Sheet 2 I Venibr 7/ fljl ffmafrfr Patented Aug. 15, 1933 PATENT OFFICE- RECORDING ACOU STIC VIBRATION Karl Pulvermacher, Budapest, Hungary, assignor of Hungary Application August 4, 1931,

and in Germany August 13,

one-half to Paul Freund,

Budapest,

Serial No. 555,027,

7 Claims. (Cl. 274-46) This invention relates to apparatus for photographically recording acoustic vibrations. The object of the invention is to provide simple and effective and novel means for recording acoustic vibrations either on the variable-area or on the variable-density principle. The invention proceeds from the known optical phenomenon that light allowed to pass through a jet of water or a bent stick of glass in longitudinal direction follows the bend and does not leave the jet or stick but at the end opposite to the entrance, as shown in Fig. 1 of the accompanying drawings. According to the invention, a stick of transparent substance, or a tube with smooth reflecting inner walls, or any other member adapted to conduct light in accordance with the above-mentioned optical phenomenon, and hereinafter referred to as a light duct to simplify expressions, is fixed at one end, and the other end thereof is set into elastic vibration in accordance with the acoustic vibrations to be recorded, a pencil of light being, at the same time, directed into the fixed end so as to pass through the light duct in longitudinal direction. This pencil of light follows the vibrations of the light duct so that when a sensitive tape, as the film of a kinematographic recording apparatus, for instance, is displaced at uniform speed in front of the vibrating end of the light duct so as to intercept the light leaving the latter, a photographic record of the mechanical vibrations corresponding to the original acoustic vibrations is produced on the sensitive tape. In this way variable-area records are obtained. The invention is, however, adapted to produce variabledensity records, too. For this purpose, a second light duct is fixed in front of the vibrating end of the said first light duct, in a way as a concatch a larger or smaller portion of the light pencil leaving the vibrating light duct according as the latter becomes more or less deflected at the moment. At the inlet end of the fixed fig ht duct, the light pencil covers, as a rule,

part only of the cross-section of the duct, but owing to dispersion in the fixed duct and reflection on the inner walls thereof, it will spread over the whole cross-section so that if the fixed light duct has a sufficient length, the

5 ler portion pencil of light leaving it' will cover the entire cross section with an intensity which will increase or decrease according as a larger or smalof the cross-section at the inlet end is illuminated at the moment. This light of tinuation thereof and in such a manner as to variable intensity will then be intercepted by the sensitive tape displaced at a uniform speed.

Electrodynamic or electrostatic methods may be used to communicate the acoustic vibrations, after their conversion into electric oscillations, to the free end of the vibrating light duct.

In order that equal communication of the different frequencies should be as little as possible interfered with by the natural frequency of 6 the light duct, two photographic records of the vibrations may, at the same time, be produced on one sensitive tape by means having light ducts of different natural frequencies of vibrations.

Some constructional examples of the invention are diagrammatically shown in the accompanying drawings in which:-

Fig. 1 shows the optical principle upon which another apparatus for variable-area records with 85 electrostatic means for communicating the vibrations to the light duct.

Figs. 6 and '7 show, in a still diagrammatic way, two more constructional examples for the simultaneous production of two sound records- 6 on one film, and Figs. 8 and 9 show each a portion of a film with the double sound records produced in accordance with Figs. 6 and '1, respectively.

Figs. 10 and 11 show how the apparatus 9.0- cording to Figs. 2 and 3 may be completed in order to produce variable-density records, and Figs. 12 shows a portion of a film with such a sound record.

Referring-first to Figs. 2 and 3, a fiat stick of glass 10 forming a light duct is secured at one end in the partition 11 of a casing, rubber pads 12 being interposed. The free end of this stick of glass 10 traverses the cylindrical body 13 of a coil. The coil sitting fast on the stick of glass has two windings 14 and 15 having no conducting connection with each other and lying each in the constant magnetic field of an electromagnet 17 and 16, respectively. An alternating current corresponding to,

known manner by means of, the acoustic vibraand produced JS in 15 at the terminals 18 and 19. The other winding 14 is short-circuited through a variable ohmic resistance 20. Two flexible arms -21 of a ring 22 embracing the coil 13 between the two windings, are fixed at their ends by means of screws 23 to the iron of the magnets or to another fixed 'part of the apparatus for the purpose of securing the coil 13 in its positions of rest.

Through a condenser lens 24 arranged in front of the fixed end of the light duct 10 a pencil of light is directed to pass through the light duct 10. In front of the free end of the light duct a set of lenses 26 is slidably disposed in a guide 25 so as to throw the light pencil leaving the light duct through a slit 27 upon the sensitive film tape 29 which is displaced at uniform speed by the sprocket-wheel 28. The length of the slit 27 is so determined and the set of lenses 26 so adjusted that, with the light duct. 10 in its position of rest, the pencil of light covers one half of the lengh of the slit. Now, whenunder the mutual action of" the alternating current supplied to the coil 15 and of the constant field of the electromagnet 16 the coil 13 together with the free end of the light duct 10 is set into vibration, then according to the amplitude and the sense of the vibrations, which take place in the direction of the arrow 30 (Fig. 3), a larger or smaller portion of the length of the slit will be covered by-the light pencil '50 that the vibrations are recorded after the'variable area principle on the film tape-29 displaced at uniform speed.

The short-circuited winding 14-of the coil 13 serves in a manner known per se for dampening 'the vibrations, which dampening may be controlled by varying the resistance 20, in order that equal communication of the difierent frequencies to the stick of glass 10 should be as little as possible interferred with by the natural vibration of the latter.

In the embodiment of the recording apparatus as shown in Fig. 5, the stick of glass 10 has its free end provided with a thin metallic coating 31 and lying-between fixed metallic armatures 32 and 33 connected with the opposite ends of the secondary Winding of a transformer 34. The acoustic vibrations to be recorded are communicated in the form of an alternating current to the primary winding of this transformer at the terminals 18 and 19. Both armatures 32 and 33 are connected through the intermediary of the secondary winding to the positive pole of a source of direct current 35,

while the metallic coating 31 of the stick of glass is connected to the negative pole of the same source of current. As long as no alternating current-is supplied to the transformer 34, the negative charge of the coating 31 is attracted with equal forces by the equal positive charges of the armatures 32 and 33 so that the light duct 10 will remain in its middle position of. rest. When, however, the equal charges of the armatures 32 and 33 are modified in opposite senses by an alternating current in the transformer 34, then the stick 10'will deflect under theaction of the increased attraction of the one or the other armature 32 or 33 to the one side or the other, i. e. it will be set into elastic vibration in accordance with the alterrating current. The optical recording of the vibrations takes place in the same manner as 'tions to be recorded is supplied to the winding hereinbefore described in connection with Figs.

2 and 3.

quencies may be still improvedby simultaneously producing two photographic records of the vibrations upon one sensitive tape bymeans of light duets with different natural vibrations. According to Figs. 6 and 8, the two sound records are produced on the two sides of the picture fields of a kinematographie film by means of light ducts 10, 10' of different lengths arranged in parallel to each other. According to Figure 7, the two light ducts 10, 10' of different lengths are arranged at an angle to each other in such a manner that the two sound records are produced side by side, as shown in Fig. 9, on the one side of the picture fields of a kinematographic film. In order that the two sound records should form an undivided strip of sound track with no interstice between them, the slits 27, 27' are staggered.

In order to obtain variable-density records, the apparatus as hereinbefore described are completed by a second light duct fixedly interposed between the vibrating end of the light duct 10 and the set of lenses 26.

Figs. 10 and 11 show such a completion of the apparatus shown in Figs. 2 and 3, the second light duct 41 being fixed in the partition 40 as a distinct continuation of the light duct 10 in its position of rest. When the light duct 10 does not vibrate, the entire pencil of light leaving the same is caught by the light duct 41. When the. light duct 10 is set into vibration, according as it becomes more or less deflected from its middle position of'rest, the inlet end of the fixed light duct 41 will receive a larger or smaller portion of the light pencil and as this larger or smaller portion of light is equally distributed over the whole cross-section of the outlet end of the fixed light duct 41, the light pencil leaving the latter and thrown by the set of lenses 26 upon the sensitivefilm 29 will .vary in intensity.

The fixed light duct 41 might be so arranged that its inlet end would catch one half only,

or another fraction, of the light pencil leaving the light duct 10 in its position of rest. The lightduct 41 or its inlet end may be adjustable in relation to the light duct 10. By such adjustment the intensity of the Whole record may be regulated.

Also a bore-hole or another aperture'in the partition 40 may serve as the fixed light-duct 41. Straightness is not an indispensable quality of the fixed light-duct 41.

What I claim is:-

1. An apparatus for photographically recording acoustic vibrations, comprising a light duct fixed at one end and adapted'to be set in elastic vibration at its other end and to conduct light in its interior from its fixed end to its free end practically without loss notwithstanding the means for displacing said tape in its longitudinal direction.

2. An apparatus forphotographically recording acoustic vibrations, comprising a light duct fixed at one end and .adapted to be set in elastic vibration at its other end and to conduct light in its interior from its fixed end to its free end practically without loss notwithstanding the a sensitive tape so arranged as tointercept the light leaving the free end of said light duct, and means for displacing said tape in its longitudinal direction.

3. An apparatus as claimed in claim 2, with electrodynamic means for setting the free end of the light duct into elastic vibration.

4. An apparatus as claimed in claim 2, with electrostatic means for setting the free end of the light duct into elastic vibration.

5. An apparatus as claimed in claim 2, with electrostatic means for setting the free end of the light duct into vibration, said electrostatic means comprising a metallic coating on the free end of the light duct, fixed metallic armatures on each side of the free end of the lightduct, a source of direct current connected with its one pole to said armatures and with its other pole to said metallic coating and means to modulate the charges of said armatures in opposite senses on opposite sides of the light duct by electric oscillations corresponding to the acoustic vibrations to be recorded.

6. An apparatus as claimed in claim 1, comprising a second light duct similar to, but having a difierent natural frequency of vibration from that of, the first one, means for setting the free end of said second light duct into elastic vibration in accordance with the acoustic vi-- brations to be recorded and simultaneously with the vibrations of the first light duct, the sensitive tape intercepting also the light leaving the second light duct.

'7. An apparatus as claimed in claim 1, comprising a second light duct similar to the first one, but entirely fixed between the sensitive tape and the free end of the first light duct in such a position as to catch and transmit towards the sensitive tape a larger or smaller portion of the light leaving the vibrating end of the first light duct according as the latter is more or less deflected at the moment.

KARL PULVERMACHER.

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